1. Field of the Invention
This invention relates to an image display method for displaying an image such as a three-dimensional image or stereoscopic image.
2. Description of the Related Art
A two-eye type stereoscopic image technique wherein both eyes of an observer observe images different from each other called parallax images to obtain a stereoscopic image and a multi-eye type stereoscopic image technique wherein a plurality of sets of parallax images are prepared to obtain a plurality of stereoscopic images from different viewpoints have already known, and various techniques relating to such techniques have been and are being developed very much. However, according to the two-eye type stereoscopic image technique or the multi-eye type stereoscopic image technique, a stereoscopic image is positioned not as a stereoscopic image in an intended space, but exists, for example, on a two-dimensional display plane and always exists at a fixed position. Accordingly, particularly convergence and adjustment which are physiologic reactions of the ophthalmencephalon do not interlink with each other, and visual fatigue caused by this makes a problem.
Meanwhile, in the real world, information of the surface of a physical solid propagates to the eyeballs of the observer through a light wave serving as a medium. As a technique by which a light wave from the surface of a physical solid physically existing in the real world can be reproduced artificially, a holography technique is available. In a stereoscopic image which uses a holography technique, interference fringes generated by interference of light are used, and a diffracted light wave front itself which is generated when light is illuminated on the interference fringes is used as an image information medium. Therefore, an image with which such physiologic reactions of the ophthalmencephalon as convergence and adjustment similar to those when the observer observes a physical solid in the real world occurs and the visual fatigue is reduced can be provided. Further, that the light wave front from the physical solid is reproduced signifies that the continuity is assured in a direction in which image information is transmitted. Accordingly, even if the viewpoint of the observer moves, it is possible to successively present an appropriate image from the different angle according to the movement, and motion parallaxes are provided successively.
However, according to the holography technique, three-dimensional spatial information of a physical solid is recorded as interference fringes in a two-dimensional space, and the amount of information is very great when compared with that of information of a two-dimensional space on a picked up photograph of the same physical solid or the like. It can be considered that this arises from the fact that, when information of a three-dimensional space is converted into information of a two-dimensional space, the information is converted into density in the two-dimensional space. Therefore, the spatial resolution required for a display device which displays interference fringes by CGH (Computer Generated Hologram) is very high, and a very great amount of information is required. Therefore, in the existing condition, it is technically difficult to implement a stereoscopic image based on a real time hologram.
In the holography technique, light waves which can be regarded as continuous information are used as an information medium to transmit information from a physical solid. Meanwhile, as a technique of discretizing light waves and using light beams to reproduce a situation theoretically substantially equivalent to a field formed from light waves in the real world to produce a stereoscopic image, a light beam reproduction method or integral photography method is known. In the light beam reproduction technique, a light beam group composed of a large number of light beams propagating in many directions is scattered into a space by optical means in advance. Then, those light beams which are to be propagated from a virtual physical solid surface disposed at an arbitrary position are selected from the light beam group, and modulation of the intensity or phase of the selected light beams is carried out to generate an image formed from the light beams in the space. An observer can observe the image as a stereoscopic image. The stereoscopic image by the light beam reproduction method is formed at an arbitrary point from multiple images from a plurality of directions and can be observed in a different manner depending upon the position from which the stereoscopic image is observed similarly as in the case wherein a three-dimensional physical solid in the real world is observed.
As an apparatus for implementing the light beam reproduction method described above, an apparatus has been proposed which utilizes a combination of a flat display apparatus such as a liquid crystal display apparatus or a plasma display apparatus and a microlens array or a pin-hole array. An apparatus of the type described is disclosed, for example, In Japanese Patent Laid-open Nos. 2003-173128, 2003-161912, 2003-295114, 2003-75771, 2002-72135 and 2001-56450 and Japanese Patent No. 3,523,605. Also an apparatus is applicable which includes a large number of projector units juxtaposed to each other. FIG. 49 shows an example of a configuration of a three-dimensional display apparatus which implements a light beam reproduction method using projector units. Referring to FIG. 49, the apparatus shown includes a large number of projector units 301 disposed in a juxtaposed relationship in a horizontal direction and a vertical direction. Light beams are emitted at different angles from the projector units 301. With the apparatus, images of multiple visual angles are multiple reproduced at an arbitrary point in a certain sectional plane 302 thereby to implement a stereoscopic image.